Polyester polymer and copolymer compositions containing metallic titanium particles

ABSTRACT

Polyester compositions are disclosed that include polyester polymers or copolymers having incorporated therein metallic titanium particles that improve the reheat properties of the compositions. Processes for making such compositions are also disclosed. The titanium particles may be incorporated in the polyester by melt compounding, or may be added at any stage of the polymerization, such as during the melt-phase of the polymerization. A range of particle sizes may be used, as well as a range of particle size distributions. The polyester compositions are suitable for use in packaging made from processes in which a reheat step is desirable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. Application Ser. No. 10/988,226 filed Nov.12, 2004 now U.S. Pat. No. 7,300,967.

FIELD OF THE INVENTION

The invention relates to polyester compositions that are useful inpackaging, such as in the manufacture of beverage containers by reheatblow molding, or other hot forming processes in which polyester isreheated. The compositions exhibit improved reheat, while maintainingacceptable visual appearance, such as clarity and color.

BACKGROUND OF THE INVENTION

Many plastic packages, such as those made from poly(ethyleneterephthalate) (PET) and used in beverage containers, are formed byreheat blow-molding, or other operations that require heat softening ofthe polymer.

In reheat blow-molding, bottle preforms, which are test-tube shapedextrusion moldings, are heated above the glass transition temperature ofthe polymer, and then positioned in a bottle mold to receive pressurizedair through their open end. This technology is well known in the art, asshown, for example in U.S. Pat. No. 3,733,309, incorporated herein byreference. In a typical blow-molding operation, radiation energy fromquartz infrared heaters is generally used to reheat the preforms.

In the preparation of packaging containers using operations that requireheat softening of the polymer, the reheat time, or the time required forthe preform to reach the proper temperature for stretch blow molding(also called the heat-up time), affects both the productivity and theenergy required. As processing equipment has improved, it has becomepossible to produce more units per unit time. Thus it is desirable toprovide polyester compositions which provide improved reheat properties,by reheating faster (increased reheat rate), or with less reheat energy(increased reheat efficiency), or both, compared to conventionalpolyester compositions.

The aforementioned reheat properties vary with the absorptioncharacteristics of the polymer itself. Heat lamps used for reheatingpolymer preforms are typically infrared heaters, such as quartz infraredlamps, having a broad light emission spectrum, with wavelengths rangingfrom about 500 nm to greater than 1,500 nm. However, polyesters,especially PET, absorb poorly in the region from 500 nm to 1,500 nm.Thus in order to maximize energy absorption from the lamps and increasethe preform's reheat rate, materials that will increase infrared energyabsorption are sometimes added to PET. Unfortunately, these materialstend to have a negative effect on the visual appearance of PETcontainers, for example increasing the haze level and/or causing thearticle to have a dark appearance. Further, since compounds withabsorbance in the range of 400-700 nm appear colored to the human eye,materials that absorb in this wavelength range will impart color to thepolymer.

A variety of black and gray body absorbing compounds have been used asreheat agents to improve the reheat characteristics of polyesterpreforms under reheat lamps. These reheat additives include carbonblack, graphite, antimony metal, black iron oxide, red iron oxide, inertiron compounds, spinel pigments, and infrared absorbing dyes. The amountof absorbing compound that can be added to a polymer is limited by itsimpact on the visual properties of the polymer, such as brightness,which may be expressed as an L* value, and color, which is measured andexpressed as an a* value and a b* value, as further described below.

To retain an acceptable level of brightness and color in the preform andresulting blown articles, the quantity of reheat additive may bedecreased, which in turn decreases reheat rates. Thus, the type andamount of reheat additive added to a polyester resin is adjusted tostrike the desired balance between increasing the reheat rate andretaining acceptable brightness and color levels.

There remains a need in the art for polyester compositions containingreheat additives that improve reheat without the problems associatedwith known reheat additives, such as unacceptable reductions inbrightness, clarity, and color.

SUMMARY OF THE INVENTION

The invention relates to polyester compositions that comprise polyesterpolymers or copolymers, and especially thermoplastic polyester polymersor copolymers, having incorporated therein metallic titanium particlesthat improve the reheat properties of the compositions. The titaniumparticles may be incorporated in the polyester by melt compounding, ormay be added at any stage of the polymerization, such as during themelt-phase of the polymerization. A range of particle sizes may be used,as well as a range of particle size distributions.

The polyester compositions according to the invention are suitable foruse in packaging in which a reheat step is desirable or necessary, andare provided with metallic titanium particles to improve reheatefficiency. These compositions may be provided as a melt, in solid form,as preforms such as for blow molding, as sheets suitable forthermoforming, as concentrates, and as bottles, the compositionscomprising a polyester polymer, with metallic titanium particlesdispersed in the polyester. Suitable polyesters include polyalkyleneterephthalates and polyalkylene naphthalates.

The invention relates also to processes for the manufacture of polyestercompositions in which metallic titanium particles may be added to anystage of a polyester polymerization process, such as during the meltphase for the manufacture of polyester polymers. The metallic titaniumparticles may also be added to the polyester polymer which is in theform of solid-stated pellets, or to an injection molding machine for themanufacture of preforms from the polyester polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform reheat improvementtemperature (RIT).

FIG. 2 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform L* value.

FIG. 3 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform a* value.

FIG. 4 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform b* value.

FIG. 5 depicts the crystallization half time (t_(1/2)) results forsystems with different levels of titanium metal particles.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of the invention, including the appendedfigures, and to the examples provided. It is to be understood that thisinvention is not limited to the specific processes and conditionsdescribed, because specific processes and process conditions forprocessing plastic articles may vary. It is also to be understood thatthe terminology used is for the purpose of describing particularembodiments only and is not intended to be limiting.

As used in the specification and the claims, the singular forms “a,”“an,” and “the” include plural referents unless the context clearlydictates otherwise. For example, reference to processing a thermoplastic“preform,” “container” or “bottle” is intended to include the processingof a plurality of thermoplastic preforms, articles, containers, orbottles.

By “comprising” or “containing” we mean that at least the namedcompound, element, particle, etc. must be present in the composition orarticle, but does not exclude the presence of other compounds,materials, particles, etc., even if the other such compounds, material,particles, etc. have the same function as what is named.

As used herein, a “d₅₀ particle size” is the median diameter, where 50%of the volume is composed of particles larger than the stated d₅₀ value,and 50% of the volume is composed of particles smaller than the statedd₅₀ value. As used herein, the median particle size is the same as thed₅₀ particle size.

According to the invention, metallic titanium particles are used toincrease the reheat rate of the compositions in which the particles aredistributed. The metallic titanium particles may comprise elementaltitanium, or may comprise one or more titanium metal alloys, the amountand nature of the alloying material not being especially critical, solong as the alloying material does not substantially affect the abilityof the resulting titanium alloy to increase the reheat rate of thepolymer compositions. Titanium and titanium alloys suitable for useaccording to the invention include those further described below and inthe “Titanium and Titanium Alloys” entry of Kirk-Othmer Encyclopedia ofChemical Technology, Vol. 24, 4th ed., (1997) pp. 186-224, incorporatedherein by reference.

The metallic titanium particles useful according to the claimedinvention may predominantly comprise, in terms of weight percent,elemental titanium metal, with typical impurities, in which the titaniummetal may be predominantly elemental titanium, or a titanium metal alloyin which titanium may be alloyed with one or more other metals,semi-metals, and/or non-metals, so long as the alloys substantiallyretain the metallic properties of titanium, and including the use ofalloy metals that result in alpha-alloy, beta-alloy, or alpha-beta alloymixtures. Thus, alloys useful according to the invention may be in theform of a single-phase alloy or a multiple phase alloy. Importantα-stabilizing alloying elements include, for example, aluminum, tin, andzirconium, and the interstitial alloying elements oxygen, nitrogen, andcarbon. Important β-stabilizing alloying elements include vanadium,molybdenum, tantalum, and niobium (all β-isomorphous), and manganese,iron, chromium, cobalt, nickel, copper, and silicon (all β-eutectoid).

Further, the phase or phases present in the metallic titanium alloyparticles according to the invention may be in the form of an amorphousphase, a solid solution phase, or an intermetallic compound phase solidsolution, and may thus be distinguished from compositions comprisedpredominantly of titanium compounds such as those in which the titaniumhas a higher oxidation state, although the alloys may, of course,include compounds of titanium that result from the alloying process,again so long as the alloys substantially retain their metallicproperties.

Alloys useful according to the invention thus include those in whichtitanium and one or more other metals or nonmetals are intimately mixedwith titanium, such as when molten, so that they are fused together anddissolved with each other to form, at least in part, a solid solution.We do not mean, of course, to exclude titanium alloys that havemeasurable amounts of carbides, nitrides, or oxides present, up to about50 wt. %, so long as such alloys retain substantial metallic properties,and in any event, the titanium present substantially retains itsmetallic properties, the presence of titanium compounds in the alloynotwithstanding.

Metals that may be alloyed with titanium in amounts up to 25 wt. %, orup to 50 wt. % or more thus include one or more of: aluminum, tin,zirconium, manganese, germanium, iron, chromium, tungsten, molybdenum,vanadium, niobium, tantalum, cobalt, nickel, palladium, ruthenium, orcopper, and especially aluminum, tin, or zirconium. Aluminum, whenpresent, may be in an amount up to about 7.5 wt. %, for example, or upto about 27 wt. %, or from about 0.5 wt. % to about 7.5 wt. %, or fromabout 0.5 wt. % to about 27 wt. %. Titanium alloys suitable for useaccording to the invention include those described in ASTM B265“Titanium and Titanium Alloy Strip, Sheet, and Plate” incorporatedherein by reference.

Metals and non-metals that can be present in minor amounts, for exampleup to about 10 wt. %, or more, include one or more of: gold, silver,copper, carbon, oxygen, nitrogen, or silicon. Alloys are thus suitablefor use according to the invention so long as such alloys comprise atleast 20 wt. % titanium metal, or at least 30 wt. % titanium, or atleast 50 wt. % titanium, or at least 60 wt. % titanium, or at least 90wt. % titanium, or at least 95 wt. % titanium, as determined, forexample, by elemental analysis, especially when the titanium is themajor alloying element. Not wishing to be bound by any theory, webelieve that the effectiveness of titanium as a reheat additive may be afunction of the absorptive properties of the titanium itself, such asthe optical constants in the wavelength of interest, so that titaniumalloys are also suitable for use according to the invention, so long assuch alloys have a significant amount of titanium, such as the minimumamounts of titanium as already described.

The metallic titanium particles may thus be elemental titanium, or maybe a titanium metal alloy in which titanium is alloyed with one or moreother materials, such as other metals, so long as such other materialsdo not substantially affect the ability of the particles to increase thereheat properties of the polymer compositions.

The titanium metal particles of the invention can be and typically willbe coated with a fine layer of titanium oxide coating, and are usefulaccording to the invention so long as the oxide coating does notsubstantially affect the ability of the titanium particles to increasethe reheat rate of the polymer compositions.

Metallic titanium particles useful according to the invention may bedistinguished from non-metallic titanium compounds, such as those inwhich the titanium is present predominantly in a higher oxidation state,including titanium (II), titanium (Ill), and titanium (IV) compounds orcomplexes. Titanium compounds are further described in Kirk-OthmerEncyclopedia of Chemical Technology, Vol 24, 4th ed., (1997) pp.225-349, incorporated herein by reference. Thus titanium compounds whichmay be used as condensation catalysts, for example titanium alkoxides orsimple chelates, are distinguishable from metallic titanium particles.That is, if non-metallic titanium compounds are used as condensationcatalysts to form the polymer in the compositions of the claimedinvention, such polymers will additionally contain metallic titaniumparticles, as further described herein.

Metallic titanium particles useful according to the invention for theimprovement of reheat and color in polyester compositions include thosehaving a range of particle sizes and particle size distributions,although we have found certain particle sizes and relatively narrowparticle size distributions to be especially suitable in certainapplications. For example, in some embodiments, especially those inwhich the polyester comprises PET, metallic titanium particles having amedian particle size of about 0.05 micrometers (μm), and a relativelynarrow particle size distribution, are advantageous.

The particles useful according to the invention may likewise be titaniumhollow spheres or titanium-coated spheres, in which the core iscomprised of titanium, of mixtures of titanium with other materials, orof other materials in the substantial absence of titanium. Again, notbeing bound by any theory, we think it likely that the effectiveness oftitanium as a reheat additive is a function of the absorptive propertiesof the titanium itself, so that titanium-coated particles are suitablefor use according to the invention, so long as the coating thickness oftitanium is sufficient to provide adequate reheat properties. Thus, invarious embodiments, the thickness of the coating may be from about0.005 μm to about 10 μm, or from 0.01 μm to 5 μm, or from 0.10 μm to 0.5μm. Such titanium coatings may also comprise titanium alloys, as alreadydescribed.

The amount of metallic titanium particles present in the polyestercompositions according to the invention may vary within a wide range,for example from about 0.5 ppm to about 1000 ppm, or from 1 ppm to 500ppm, or from 5 ppm to 100 ppm, or from 5 ppm to 50 ppm. Thermoplasticconcentrates according to the invention may, of course, have amountsgreater than these, as further described elsewhere herein.

We note that titanium metal particles can be produced by numeroustechniques, as described in the Powder Metallurgy entry in Kirk-OthmerEncyclopedia of Chemical Technology, Vol 16, 4th ed., (1995) pp. 353-392, incorporated herein by reference. For example, the titanium metalparticles according to the invention may be formed by atomization,reduction, decomposition, electrolytic deposition, precipitation,electrode spinning, high energy impaction, mechanical comminution,condensation, decomposition of metal hydrides, or rapid solidificationtechnology.

In the atomization technique, a stream of molten metal is struck withwater or air jet and the particles formed are collected, sieved, andannealed. In the reduction method, metal oxide is reduced in a solid orgaseous media. The decomposition method produces a fine powder of metalby the decomposition of liquid or gaseous carbonyls. Electrolyticdecomposition from molten salts or solutions produces metal powderdirectly, or else produces an adherent mass that may be mechanicallycomminuted. In the precipitation process, titanium ammonium carbonategives titanium powder when subjected to hydrogen in an autoclave. In theelectrode spinning method, molten metal droplets are produced that arecentrifuged in a closed chamber. In the high energy impact method,brittle coarse shapes are impinged against a tungsten carbide target athigh velocities. Mechanical comminution techniques can producerelatively coarse particles by machining, or can produce fine particlesby methods such as ball milling, impact milling, gyratory crushing, oreddy milling. Metal powders can be formed by condensation of metalvapors on cool surfaces. Metal hydrides can be decomposed by vacuumtreatment to give powders of fine particle sizes. In rapidsolidification technology, molten metal is quench cast as a continuousribbon which is subsequently pulverized to an amorphous powder.

Shapes of metallic titanium powder which can be used in this inventioninclude, but are not limited to, the following: acicular powder, angularpowder, dendritic powder, equi-axed powder, flake powder, fragmentedpowder, granular powder, irregular powder, nodular powder, plateletpowder, porous powder, rounded powder, and spherical powder. Theparticles may be of a filamentary structure, where the individualparticles may be loose aggregates of smaller particles attached to forma bead or chain-like structure. The overall size of the particles may bevariable, due to a variation in chain length and degree of branching.

The size of the metallic titanium particles may thus vary within a broadrange depending on the method of production, and the numerical valuesfor the particle sizes may vary according to the shape of the particlesand the method of measurement. Particle sizes useful according to theinvention may be from about 0.005 μm to about 100 μm, or from 0.01 μm to10 μm, or from 0.01 μm to 5 μm. When the polyester composition comprisesPET, we have found that particle sizes from 0.01 μm to 5 μm areespecially suitable. Metal particles, which have a mean particle sizesuitable for the invention, may have irregular shapes and formchain-like structures, although roughly spherical particles may bepreferred. The particle size and particle size distribution may bemeasured by methods such as those described in the Size Measurement ofParticles entry of Kirk-Othmer Encyclopedia of Chemical Technology, Vol.22, 4th ed., (1997) pp. 256-278, incorporated herein by reference. Forexample, particle size and particle size distributions may be determinedusing a Fisher Subsieve Sizer or a Microtrac Particle-Size Analyzermanufactured by Leeds and Northrop Company, or by microscopictechniques, such as scanning electron microscopy or transmissionelectron microscopy.

A range of particle size distributions may be useful according to theinvention. The particle size distribution, as used herein, may beexpressed by “span (S),” where S is calculated by the followingequation:

$S = \frac{d_{90} - d_{10}}{d_{50}}$where d₉₀ represents a particle size in which 90% of the volume iscomposed of particles smaller than the stated d₉₀; and d₁₀ represents aparticle size in which 10% of the volume is composed of particlessmaller than the stated d₁₀; and d₅₀ represents a particle size in which50% of the volume is composed of particles larger than the stated d₅₀value, and 50% of the volume is composed of particles smaller than thestated d₅₀ value.

Thus, particle size distributions in which the span (S) is from 0 to 10,or from 0 to 5, or from 0.01 to 2, may be used according to theinvention.

In order to obtain a good dispersion of metallic titanium particles inthe polyester compositions, a concentrate, containing for example about500 ppm to about 1,000 ppm metallic titanium particles, may be preparedusing a polyester such as a commercial grade of PET. The concentrate maythen be let down into a polyester at the desired concentration, ranging,for example, from 1 ppm to 500 ppm.

The amount of metallic titanium particles used in the polyester willdepend upon the particular application, the desired reduction in reheattime, and the toleration level in the reduction of a* and b* away fromzero along with the movement of L* brightness values away from 100.Thus, in various embodiments, the quantity of metallic titaniumparticles may be at least 0.5 ppm, or at least 1 ppm, or at least 5 ppm.In many applications, the quantity of metallic titanium particles may beat least 50 ppm, in some cases at least 60 ppm, and even at least 70ppm. The maximum amount of metallic titanium particles may be limited byone or more of the desired reheat rate, or maintenance in L*, a*, b* andother color properties, which may vary among applications or customerrequirements. In some embodiments, the amount may not exceed 500 ppm, ormay be at or below 300 ppm, or may not exceed 250 ppm. In thoseapplications where color, haze, and brightness are not importantfeatures to the application, however, the amount of metallic titaniumparticles used may be up to 1,000 ppm, or up to 5,000 ppm, or even up to10,000 ppm. The amount can even exceed 10,000 ppm when formulating aconcentrate with metallic titanium particles as discussed elsewhereherein.

The method by which the metallic titanium particles are incorporatedinto the polyester composition is not limited. The metallic titaniumparticles can be added to the polymer reactant system, during or afterpolymerization, to the polymer melt, or to the molding powder or pelletsor molten polyester in the injection-molding machine from which thebottle preforms are made. They may be added at locations including, butnot limited to, proximate the inlet to the esterification reactor,proximate the outlet of the esterification reactor, at a point betweenthe inlet and the outlet of the esterification reactor, anywhere alongthe recirculation loop, proximate the inlet to the prepolymer reactor,proximate the outlet to the prepolymer reactor, at a point between theinlet and the outlet of the prepolymer reactor, proximate the inlet tothe polycondensation reactor, or at a point between the inlet and theoutlet of the polycondensation reactor.

The metallic titanium particles may be added to a polyester polymer,such as PET, and fed to an injection molding machine by any method,including feeding the metallic titanium particles to the molten polymerin the injection molding machine, or by combining the metallic titaniumparticles with a feed of PET to the injection molding machine, either bymelt blending or by dry blending pellets.

Alternatively, the metallic titanium particles may be added to anesterification reactor, such as with and through the ethylene glycolfeed optionally combined with phosphoric acid, to a prepolymer reactor,to a polycondensation reactor, or to solid pellets in a reactor forsolid stating, or at any point in-between any of these stages. In eachof these cases, the metallic titanium particles may be combined with PETor its precursors neat, as a concentrate containing PET, or diluted witha carrier. The carrier may be reactive to PET or may be non-reactive.The metallic titanium particles, whether neat or in a concentrate or ina carrier, and the bulk polyester, may be dried prior to mixingtogether. These may be dried in an atmosphere of dried air or otherinert gas, such as nitrogen, and if desired, under sub-atmosphericpressure.

The impact of a reheat additive on the color of the polymer can bejudged using a tristimulus color scale, such as the CIE L*a*b* scale.The L* value ranges from 0 to 100 and measures dark to light. The a*value measures red to green with positive values being red and negativevalues green. The b* value measures yellow to blue with yellow havingpositive values and blue negative values.

Color measurement theory and practice are discussed in greater detail inPrinciples of Color Technology, pp. 25-66 by Fred W. Billmeyer, Jr.,John Wiley & Sons, New York (1981), incorporated herein by reference.

L* values for the polyester compositions as measured on twenty-ouncebottle preforms discussed herein should generally be greater than 60,more preferably at least 65, and more preferably yet at least 70.Specifying a particular L* brightness does not imply that a preformhaving a particular sidewall cross-sectional thickness is actually used,but only that in the event the L* is measured, the polyester compositionactually used is, for purposes of testing and evaluating the L* of thecomposition, injection molded to make a preform having a sidewallcross-sectional thickness of 0.154 inches.

The color of a desirable polyester composition, as measured intwenty-ounce bottle preforms having a nominal sidewall cross-sectionalthickness of 0.154 inches, is generally indicated by an a* coordinatevalue preferably ranging from about minus 1.9 to about plus 0.5 or fromabout minus 1.5 to about plus 0.2. With respect to a b* coordinatevalue, it is generally desired to make a bottle preform having a b*value coordinate ranging from minus 3.0, or from minus 0.1 to positivevalue of less than plus 5.0, or less than plus 4.0, or less than plus3.8, or less than 2.6.

The measurements of L*, a* and b* color values are conducted accordingto the following method. The instrument used for measuring b* colorshould have the capabilities of a HunterLab UltraScan XE, model U3350,using the CIE Lab Scale (L*, a*, b*), D65 (ASTM) illuminant, 10°observer and an integrating sphere geometry. Clear plaques, films,preforms, bottles, and are tested in the transmission mode under ASTMD1746 “Standard Test Method for Transparency of Plastic Sheeting.” Theinstrument for measuring color is set up under ASTM E1164 “StandardPractice for Obtaining Spectrophotometric Data for Object-ColorEvaluation.”

More particularly, the following test methods can be used, dependingupon whether the sample is a preform, or a bottle. Color measurementsshould be performed using a HunterLab UltraScan XE (Hunter AssociatesLaboratory, Inc., Reston Va.), which employs diffuse/8°(illumination/view angle) sphere optical geometry, or equivalentequipment with these same basic capabilities. The color scale employedis the CIE L*a*b* scale with D65 illuminant and 10° observer specified.

Preforms having a mean outer diameter of 0.846 inches and a wallthickness of 0.154 inches are measured in regular transmission modeusing ASTM D1746, “Standard Test Method for Transparency of PlasticSheeting”. Preforms are held in place in the instrument using a preformholder, available from HunterLab, and triplicate measurements areaveraged, whereby the sample is rotated 90° about its center axisbetween each measurement.

The intrinsic viscosity (It.V.) values described throughout thisdescription are set forth in dL/g unit as calculated from the inherentviscosity (Ih.V.) measured at 25° C. in 60/40 wt/wtphenol/tetrachloroethane. The inherent viscosity is calculated from themeasured solution viscosity. The following equations describe thesesolution viscosity measurements, and subsequent calculations to Ih.V.and from Ih.V. to It.V:η_(inh) =[ln(t _(s) /t _(o))]/C

-   -   where η_(inh)=Inherent viscosity at 25° C. at a polymer        concentration of 0.50 g/100 mL of 60% phenol and 40% 1,1        ,2,2-tetrachloroethane        -   ln=Natural logarithm        -   ts=Sample flow time through a capillary tube        -   to=Solvent-blank flow time through a capillary tube        -   C=Concentration of polymer in grams per 100 mL of solvent            (0.50%)

The intrinsic viscosity is the limiting value at infinite dilution ofthe specific viscosity of a polymer. It is defined by the followingequation:

$\eta_{int} = {{\lim\limits_{C\rightarrow 0}\left( {\eta_{sp}/C} \right)} = {\lim\limits_{C\rightarrow 0}\mspace{11mu}{\ln\left( {\eta_{r}/C} \right)}}}$

-   -   where η_(int)=Intrinsic viscosity        -   η_(r)=Relative viscosity=ts/to        -   η_(sp)=Specific viscosity=η_(r)−1

Instrument calibration involves replicate testing of a standardreference material and then applying appropriate mathematical equationsto produce the “accepted” I.V. values.

-   -   Calibration Factor=Accepted IV of Reference Material/Average of        Replicate Determinations    -   Corrected IhV=Calculated IhV× Calibration Factor    -   The intrinsic viscosity (It.V. or η_(int)) may be estimated        using the

Billmeyer equation as follows:η_(int)=0.5[e ^(0.5)×Corrected Ihv−1]+(0.75×Corrected IhV)

Thus, a beneficial feature provided by polyester compositions containingtitanium nitride particles is that the compositions and preforms madefrom these compositions have an improved reheat rate, expressed as atwenty-ounce bottle preform Reheat Improvement Temperature (RIT),relative to a control sample with no reheat additive. The following testfor RIT is used herein, in order to determine the reheat rate, or RIT,of the compositions described and claimed. Twenty-ounces preforms (withan outer diameter of 0.846 inches and a sidewall cross-sectionalthickness of 0.154 inches) are run through the oven bank of a SidelSBO2/3 blow molding unit. The lamp settings for the Sidel blow moldingunit are shown in Table 1. The preform heating time in the heaters is 38seconds, and the power output to the quartz infrared heaters is set at64%.

TABLE 1 Sidel SBO2/3 lamp settings. Lamps ON = 1 OFF = 0 Heating Lamppower zone setting (%) Heater 1 Heater 2 Heater 3 Zone 8 zone 7 Zone 6Zone 5 90 1 0 1 Zone 4 90 1 0 1 Zone 3 90 1 0 1 Zone 2 90 1 0 1 Zone 190 1 1 1

In the test, a series of five twenty-ounce bottle preforms is passed infront of the quartz infrared heaters and the preform surface temperatureis measured. All preforms are tested in a consistent manner. The preformreheat improvement temperature (RIT) is then calculated by comparing thedifference in preform surface temperature of the target samplescontaining a reheat additive with that of the same polymer having noreheat additive. The higher the RIT value, the higher the reheat rate ofthe composition.

Thus, in various embodiments, the twenty-ounce bottle preform reheatimprovement temperature (RIT) of the polyester compositions according tothe claimed invention containing titanium nitride particles, may be fromabout 0.1° C. to about 3° C., or from 1° C. to 14° C.

In some embodiments, the polyester compositions containing metallictitanium particles, and preforms made from these compositions, may havea b* color of less than 4, or less than 3, and in any case greater thanminus 3, at loadings ranging from 2 ppm to 15 ppm. Similarly, preformsfrom the polyester compositions according to the invention may have anL* brightness of at least 60.

According to the invention, in various embodiments, there are thusprovided concentrate compositions comprising metallic titanium particlesin an amount of at least 0.05 wt. %, or at least 2 wt. %, and up toabout 20 wt. %, or up to 35 wt. %, and a thermoplastic polymer normallysolid at 25° C. and 1 atm such as a polyester, polyolefin, orpolycarbonate in an amount of at least 65 wt. %, or at least 80 wt. %,or up to 99 wt. % or more, each based on the weight of the concentratecomposition. The concentrate may be in liquid, molten state, or solidform. The converter of polymer to preforms has the flexibility of addingmetallic titanium particles to bulk polyester at the injection moldingstage continuously, or intermittently, in liquid molten form or as asolid blend, and further adjusting the amount of metallic titaniumparticles contained in the preform by metering the amount of concentrateto fit the end use application and customer requirements.

The concentrate may be made by mixing metallic titanium particles with apolymer such as a polycarbonate, a polyester, a polyolefin, or mixturesof these, in a single or twin-screw extruder, and optionally compoundingwith other reheat additives. A suitable polycarbonate is bisphenol Apolycarbonate. Suitable polyolefins include, but not limited to,polyethylene and polypropylene, and copolymers thereof. Melttemperatures should be at least as high as the melting point of thepolymer. For a polyester, such as PET, the melt temperatures aretypically in the range of 250°-310° C. Preferably, the melt compoundingtemperature is maintained as low as possible. The extrudate may bewithdrawn in any form, such as a strand form, and recovered according tothe usual way such as cutting.

The concentrate may be prepared in a similar polyester as used in thefinal article. However, in some cases it may be advantageous to useanother polymer in the concentrate, such as a polyolefin. In the casewhere a polyolefin/metallic titanium particles concentrate is blendedwith the polyester, the polyolefin can be incorporated as a nucleatoradditive for the bulk polyester.

The concentrate may be added to a bulk polyester or anywhere along thedifferent stages for manufacturing PET, in a manner such that theconcentrate is compatible with the bulk polyester or its precursors. Forexample, the point of addition or the It.V. of the concentrate may bechosen such that the It.V. of the polyethylene terephthalate and theIt.V. of the concentrate are similar, e.g. +/−0.2 It.V. measured at 25°C. in a 60/40 wt/wt phenol/tetrachloroethane solution. A concentrate canbe made with an It.V. ranging from 0.3 dL/g to 1.1 dL/g to match thetypical It.V. of a polyethylene terephthalate under manufacture in thepolycondensation stage. Alternatively, a concentrate can be made with anIt.V. similar to that of solid-stated pellets used at the injectionmolding stage (e.g. lt.V. from 0.6 dL/g to 1.1 dL/g).

Other components can be added to the polymer compositions of the presentinvention to enhance the performance properties of the polyestercomposition. For example, crystallization aids, impact modifiers,surface lubricants, denesting agents, stabilizers, antioxidants,ultraviolet light absorbing agents, catalyst deactivators, colorants,nucleating agents, acetaldehyde reducing compounds, other reheatenhancing aids, fillers, anti-abrasion additives, and the like can beincluded. The resin may also contain small amounts of branching agentssuch as trifunctional or tetrafunctional comonomers such as trimelliticanhydride, trimethylol propane, pyromellitic dianhydride,pentaerythritol, and other polyester forming polyacids or polyolsgenerally known in the art. All of these additives and many others andtheir use are well known in the art. Any of these compounds can be usedin the present composition.

The polyester compositions of the present invention may be used to formpreforms used for preparing packaging containers. The preform istypically heated above the glass transition temperature of the polymercomposition by passing the preform through a bank of quartz infraredheating lamps, positioning the preform in a bottle mold, and thenblowing pressurized air through the open end of the mold.

A variety of other articles can be made from the polyester compositionsof the invention. Articles include sheet, film, bottles, trays, otherpackaging, rods, tubes, lids, and injection molded articles. Any type ofbottle can be made from the polyester compositions of the invention.Thus, in one embodiment, there is provided a beverage bottle made fromPET suitable for holding water. In another embodiment, there is provideda heat-set beverage bottle suitable for holding beverages which arehot-filled into the bottle. In yet another embodiment, the bottle issuitable for holding carbonated soft drinks.

The metallic titanium particle reheat additives used in the inventionaffect the reheat rate, brightness and color of preforms. Any one ormore of these performance characteristics may be adjusted by varying theamount of reheat additive used, or by changing the particle size, or theparticle size distribution.

The invention also provides processes for making polyester preforms thatcomprise feeding a liquid or solid bulk polyester and a liquid, moltenor solid polyester concentrate composition to a machine formanufacturing the preform, the concentrate being as described elsewhere.According to the invention, not only may the concentrate be added at thestage for making preforms, but in other embodiments, there are providedprocesses for the manufacture of polyester compositions that compriseadding a concentrate polyester composition to a melt phase for themanufacture of virgin polyester polymers, the concentrate comprisingmetallic titanium particles and at least 65 wt. % of a polyesterpolymer. Alternatively, the titanium particles may be added to recycledPET.

The polyester compositions according to the invention have a good reheatrate with acceptable color properties.

In yet another embodiment of the invention, there is provided apolyester beverage bottle made from a preform, wherein the preform has areheat improvement temperature (RIT) of 10° C. or more at a preform L*value of 70 or more.

In each of the described embodiments, there are also provided additionalembodiments encompassing the processes for the manufacture of each, andthe preforms and articles, and in particular bottles, blow-molded fromthe preforms, as well as their compositions containing metallic titaniumparticles.

The polyester compositions of this invention may be any thermoplasticpolymers, optionally containing any number of ingredients in anyamounts, provided that the polyester component of the polymer is presentin an amount of at least 30 wt. %, or at least 50 wt. %, or at least 80wt. %, or even 90 wt. % or more, based on the weight of the polymer, thebackbone of the polymer typically including repeating terephthalate ornaphthalate units.

Examples of suitable polyester polymers include one or more of: PET,polyethylene naphthalate (PEN), poly(1,4-cyclo-hexylenedimethylene)terephthalate (PCT), poly(ethylene-co-1,4-cyclohexanedimethyleneterephthalate) (PETG), copoly(1,4-cyclohexylene dimethylene/ethyleneterephthalate) (PCTG) and their blends or their copolymers. The form ofthe polyester composition is not limited, and includes a melt in themanufacturing process or in the molten state after polymerization, suchas may be found in an injection molding machine, and in the form of aliquid, pellets, preforms, and/or bottles. Polyester pellets may beisolated as a solid at 25° C. and 1 atm in order for ease of transportand processing. The shape of the polyester pellet is not limited, and istypified by regular or irregular shaped discrete particles and may bedistinguished from a sheet, film, or fiber.

It should also be understood that as used herein, the term polyester isintended to include polyester derivatives, including, but not limitedto, polyether esters, polyester amides, and polyetherester amides.Therefore, for simplicity, throughout the specification and claims, theterms polyester, polyether ester, polyester amide, and polyetheresteramide may be used interchangeably and are typically referred to aspolyester, but it is understood that the particular polyester species isdependant on the starting materials, i.e., polyester precursor reactantsand/or components.

The location of the metallic titanium particles within the polyestercompositions is not limited. The metallic titanium particles may bedisposed anywhere on or within the polyester polymer, pellet, preform,or bottle. Preferably, the polyester polymer in the form of a pelletforms a continuous phase. By being distributed “within” the continuousphase we mean that the metallic titanium particles are found at leastwithin a portion of a cross-sectional cut of the pellet. The metallictitanium particles may be distributed within the polyester polymerrandomly, distributed within discrete regions, or distributed onlywithin a portion of the polymer. In a preferred embodiment, the metallictitanium particles are disposed randomly throughout the polyesterpolymer composition as by way of adding the metallic titanium particlesto a melt, or by mixing the metallic titanium particles with a solidpolyester composition followed by melting and mixing.

The metallic titanium particles may be added in an amount so as toachieve a twenty-ounce bottle preform reheat improvement temperature(RIT) of at least 3° C., or at least 5° C., or at least 10° C., whilemaintaining acceptable preform color properties.

Suitable amounts of metallic titanium particles in the polyestercompositions ppm, based on the weight of the polymer in the polyestercompositions, or performs, and containers, may thus range from about 0.5ppm to about 500 ppm, based on the weight of the polymer in thepolyester compositions, or as already described. The amount of themetallic titanium particles used may depend on the type and quality ofthe metallic titanium particles, the particle size, surface area, themorphology of the particle, and the level of reheat rate improvementdesired.

The particle size may be measured with a laser diffraction type particlesize distribution meter, or scanning or transmission electron microscopymethods. Alternatively, the particle size can be correlated by apercentage of particles screened through a mesh. Metallic titaniumparticles having a particle size distribution in which at least 80%,preferably at least 90%, more preferably at least 95% of the particlesfall through an ASTM-E11 140 sieve are suitable for use as reheatagents. Metallic titanium particles having a particle size distributionin which at least 80%, preferably at least 90%, more preferably at least95% of the particles fall through a ASTM-E11 325 sieve are also suitablefor use as reheat agents.

The metallic titanium particles used in the invention not only enhancethe reheat rate of a preform, but have only a minimal impact on thebrightness of the preforms and bottles by not reducing the L* belowacceptable levels. An acceptable L* value of preforms is deemed 60 ormore when measured at a twenty-ounce bottle preform reheat improvementtemperature (RIT) of 10° C.

In various other embodiments, there are provided polyester compositions,whether in the form of a melt, pellets, sheets, preforms, and/orbottles, comprising at least 0.5 ppm, or at least 50 ppm, or at least100 ppm metallic titanium particles, having a d₅₀ particle size of lessthan 100 μm, or less than 50 μm, or less than 1 μm or less, wherein thepolyester compositions have a preform L* value of 60 or more, or 68 ormore, or even 70 or more, when measured at a RIT of 13° C., or 10° C.,or 9° C.

According to various embodiments of the invention, metallic titaniumparticles may be added at any point during polymerization, whichincludes to the esterification zone, to the polycondensation zonecomprised of the prepolymer zone and the finishing zone, to or prior tothe pelletizing zone, and at any point between or among these zones. Themetallic titanium particles may also be added to solid-stated pellets asthey are exiting the solid-stating reactor. Furthermore, metallictitanium particles may be added to the PET pellets in combination withother feeds to the injection molding machine, or may be fed separatelyto the injection molding machine. For clarification, the metallictitanium particles may be added in the melt phase or to an injectionmolding machine without solidifying and isolating the polyestercomposition into pellets. Thus, the metallic titanium particles can alsobe added in a melt-to-mold process at any point in the process formaking the preforms. In each instance at a point of addition, themetallic titanium particles can be added as a powder neat, or in aliquid, or a polymer concentrate, and can be added to virgin or recycledPET, or added as a polymer concentrate using virgin or recycled PET asthe PET polymer carrier.

In other embodiments, the invention relates to processes for themanufacture of polyester compositions containing metallic titaniumparticles, such as polyalkylene terephthalate or naphthalate polymersmade by transesterifying a dialkyl terephthalate or dialkyl naphthalateor by directly esterifying terephthalic acid or naphthalene dicarboxylicacid.

Thus, there are provided processes for making polyalkylene terephthalateor naphthalate polymer compositions by transesterifying a dialkylterephthalate or naphthalate or directly esterifying a terephthalic acidor naphthalene dicarboxylic acid with a diol, adding metallic titaniumparticles to the melt phase for the production of a polyalkyleneterephthalate or naphthalate after the prepolymer zone, or topolyalkylene terephthalate or naphthalate solids, or to an injectionmolding machine for the manufacture of bottle preforms.

Each of these process embodiments, along with a description of thepolyester polymers, is now explained in further detail.

The polyester polymer may be PET, PEN, or copolymers or mixtures,thereof. A preferred polyester polymer is polyethylene terephthalate. Asused herein, a polyalkylene terephthalate polymer or polyalkylenenaphthalate polymer means a polymer having polyalkylene terephthalateunits or polyalkylene naphthalate units in an amount of at least 60 mole% based on the total moles of units in the polymer, respectively. Thus,the polymer may contain ethylene terephthalate or naphthalate units inan amount of at least 85 mole %, or at least 90 mole %, or at least 92mole %, or at least 96 mole %, as measured by the mole % of ingredientsadded to the reaction mixture. Thus, a polyethylene terephthalatepolymer may comprise a copolyester of ethylene terephthalate units andother units derived from an alkylene glycol or aryl glycol with analiphatic or aryl dicarboxylic acid.

While reference is made in certain instances to polyethyleneterephthalate, it is to be understood that the polymer may also be apolyalkylene naphthalate polymer.

Polyethylene terephthalate can be manufactured by reacting a diacid ordiester component comprising at least 60 mole % terephthalic acid orC₁-C₄ dialkylterephthalate, or at least 70 mole %, or at least 85 mole%, or at least 90 mole %, and for many applications at least 95 mole %,and a diol component comprising at least 60 mole % ethylene glycol, orat least 70 mole %, or at least 85 mole %, or at least 90 mole %, andfor many applications, at least 95 mole %. It is preferable that thediacid component is terephthalic acid and the diol component is ethyleneglycol. The mole percentage for all the diacid component(s) totals 100mole %, and the mole percentage for all the diol component(s) totals 100mole %.

The polyester pellet compositions may include admixtures of polyalkyleneterephthalates, PEN, or mixtures thereof, along with other thermoplasticpolymers, such as polycarbonates and polyamides. It is preferred in manyinstances that the polyester composition comprise a majority of apolyalkylene terephthalate polymers or PEN polymers, or in an amount ofat least 80 wt. %, or at least 95 wt. %, based on the weight of polymers(excluding fillers, compounds, inorganic compounds or particles, fibers,impact modifiers, or other polymers which may form a discontinuousphase). In addition to units derived from terephthalic acid, the acidcomponent of the present polyester may be modified with, or replaced by,units derived from one or more other dicarboxylic acids, such asaromatic dicarboxylic acids preferably having from 8 to 14 carbon atoms,aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, orcycloaliphatic dicarboxylic acids preferably having 8 to 12 carbonatoms. Examples of dicarboxylic acid units useful for the acid componentare units from phthalic acid, isophthalic acid,naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid,cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid, succinicacid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and thelike, with isophthalic acid, naphthalene-2,6-dicarboxylic acid, andcyclohexanedicarboxylic acid being preferable.

It should be understood that use of the corresponding acid anhydrides,esters, and acid chlorides of these acids is included in the term“dicarboxylic acid”.

In addition to units derived from ethylene glycol, the diol component ofthe present polyester may be modified with, or replaced by, units fromadditional diols including cycloaliphatic diols preferably having 6 to20 carbon atoms and aliphatic diols preferably having 2 to 20 carbonatoms. Examples of such diols include diethylene glycol (DEG);triethylene glycol; 1,4-cyclohexaned imethanol; propane-1,3-diol;butane-1,4-d iol; pentane-1,5-diol; hexane-1,6-diol;3-methylpentanediol-(2,4); 2-methylpentanediol-(1,4);2,2,4-trimethylpentane-diol-(1,3); 2,5-ethylhexanediol-(1,3);2,2-diethyl propane-diol-(1,3); hexanediol-(1,3);1,4-di-(hydroxyethoxy)-benzene; 2,2-bis-(4-hydroxycyclohexyl)-propane;2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane.

The polyester compositions of the invention may be prepared byconventional polymerization procedures well-known in the art sufficientto effect esterification and polycondensation. Polyester melt phasemanufacturing processes include direct condensation of a dicarboxylicacid with a diol optionally in the presence of esterification catalystsin the esterification zone, followed by polycondensation in theprepolymer and finishing zones in the presence of a polycondensationcatalyst; or else ester interchange usually in the presence of atransesterification catalyst in the esterification zone, followed byprepolymerization and finishing in the presence of a polycondensationcatalyst, and each may optionally be subsequently solid-stated accordingto known methods. After melt phase and/or solid-state polycondensationthe polyester polymer compositions typically have an intrinsic viscosity(It.V.) ranging from 0.55 dL/g to about 0.70 dL/g as precursor pellets,and an lt.V. ranging from about 0.70 dL/g to about 1.1 dL/g for solidstated pellets.

To further illustrate, a mixture of one or more dicarboxylic acids,preferably aromatic dicarboxylic acids, or ester forming derivativesthereof, and one or more diols, are continuously fed to anesterification reactor operated at a temperature of between about 200°C. and 300° C., typically between 240° C. and 290° C., and at a pressureof about 1 psig up to about 70 psig. The residence time of the reactantstypically ranges from between about one and five hours. Normally, thedicarboxylic acid is directly esterified with diol(s) at elevatedpressure and at a temperature of about 240° C. to about 270° C. Theesterification reaction is continued until a degree of esterification ofat least 60% is achieved, but more typically until a degree ofesterification of at least 85% is achieved to make the desired monomer.The esterification monomer reaction is typically uncatalyzed in thedirect esterification process and catalyzed in transesterificationprocesses. Polycondensation catalysts may optionally be added in theesterification zone along with esterification/transesterificationcatalysts.

Typical esterification/transesterification catalysts which may be usedinclude titanium alkoxides, dibutyl tin dilaurate, used separately or incombination, optionally with zinc, manganese, or magnesium acetates orbenzoates and/or other such catalyst materials as are well known tothose skilled in the art. Phosphorus-containing compounds and cobaltcompounds may also be present in the esterification zone. The resultingproducts formed in the esterification zone include bis(2-hydroxyethyl)terephthalate (BHET) monomer, low molecular weight oligomers, DEG, andwater as the condensation by-product, along with other trace impuritiesformed by the reaction of the catalyst and other compounds such ascolorants or the phosphorus-containing compounds. The relative amountsof BHET and oligomeric species will vary depending on whether theprocess is a direct esterification process, in which case the amount ofoligomeric species are significant and even present as the majorspecies, or a transesterification process, in which case the relativequantity of BHET predominates over the oligomeric species. The water isremoved as the esterification reaction proceeds and excess ethyleneglycol is removed to provide favorable equilibrium conditions. Theesterification zone typically produces the monomer and oligomer mixture,if any, continuously in a series of one or more reactors. Alternatively,the monomer and oligomer mixture could be produced in one or more batchreactors.

It is understood, however, that in a process for making PEN, thereaction mixture will contain monomeric species such asbis(2-hydroxyethyl) naphthalate and its corresponding oligomers. Oncethe ester monomer is made to the desired degree of esterification, it istransported from the esterification reactors in the esterification zoneto the polycondensation zone comprised of a prepolymer zone and afinishing zone.

Polycondensation reactions are initiated and continued in the melt phasein a prepolymerization zone and finished in the melt phase in afinishing zone, after which the melt may be solidified into precursorsolids in the form of chips, pellets, or any other shape. Forconvenience, solids are referred to as pellets, but it is understoodthat a pellet can have any shape, structure, or consistency. If desired,the polycondensation reaction may be continued by solid-stating theprecursor pellets in a solid-stating zone.

Although reference is made to a prepolymer zone and a finishing zone, itis to be understood that each zone may comprise a series of one or moredistinct reaction vessels operating at different conditions, or thezones may be combined into one reaction vessel using one or moresub-stages operating at different conditions in a single reactor. Thatis, the prepolymer stage can involve the use of one or more reactorsoperated continuously, one or more batch reactors or even one or morereaction steps or sub-stages performed in a single reactor vessel. Insome reactor designs, the prepolymerization zone represents the firsthalf of polycondensation in terms of reaction time, while the finishingzone represents the second half of polycondensation. While other reactordesigns may adjust the residence time between the prepolymerization zoneto the finishing zone at about a 2:1 ratio, a common distinction in alldesigns between the prepolymerization zone and the finishing zone isthat the latter zone operates at a higher temperature, lower pressure,and a higher surface renewal rate than the operating conditions in theprepolymerization zone. Generally, each of the prepolymerization and thefinishing zones comprise one or a series of more than one reactionvessel, and the prepolymerization and finishing reactors are sequencedin a series as part of a continuous process for the manufacture of thepolyester polymer.

In the prepolymerization zone, also known in the industry as the lowpolymerizer, the low molecular weight monomers and minor amounts ofoligomers are polymerized via polycondensation to form polyethyleneterephthalate polyester (or PEN polyester) in the presence of acatalyst. If the catalyst was not added in the monomer esterificationstage, the catalyst is added at this stage to catalyze the reactionbetween the monomers and low molecular weight oligomers to formprepolymer and split off the diol as a by-product. If a polycondensationcatalyst was added to the esterification zone, it is typically blendedwith the diol and fed into the esterification reactor as the diol feed.Other compounds such as phosphorus-containing compounds, cobaltcompounds, and colorants can also be added in the prepolymerizationzone. These compounds may, however, be added in the finishing zoneinstead of or in addition to the prepolymerization zone.

In a typical DMT-based process, those skilled in the art recognize thatother catalyst material and points of adding the catalyst material andother ingredients vary from a typical direct esterification process.

Typical polycondensation catalysts include the compounds of antimony,titanium, germanium, zinc and tin in an amount ranging from 0.1 ppm to1,000 ppm based on the weight of resulting polyester polymer. A commonpolymerization catalyst added to the prepolymerization zone is anantimony-based polymerization catalyst. Suitable antimony-basedcatalysts include antimony (III) and antimony (V) compounds recognizedin the art, and in particular, diol-soluble antimony (III) and antimony(V) compounds with antimony (III) being most commonly used. Othersuitable compounds include those antimony compounds that react with, butare not necessarily soluble in, the diols, with examples of suchcompounds including antimony (III) oxide. Specific examples of suitableantimony catalysts include antimony (III) oxide and antimony (III)acetate, antimony (III) glycolates, antimony (III) ethyleneglycoxide andmixtures thereof, with antimony (III) oxide being preferred. Thepreferred amount of antimony catalyst added is that effective to providea level of between about 75 ppm and about 400 ppm of antimony by weightof the resulting polyester.

This prepolymer polycondensation stage generally employs a series of twoor more vessels and is operated at a temperature of between about 250°C. and 305° C. for between about one and four hours. During this stage,the It.V. of the monomers and oligomers is typically increased up toabout no more than 0.35 dL/g. The diol byproduct is removed from theprepolymer melt using an applied vacuum ranging from 15 torr to 70 torrto drive the reaction to completion. In this regard, the polymer melt istypically agitated to promote the escape of the diol from the polymermelt and to assist the highly viscous polymer melt in moving through thepolymerization vessels. As the polymer melt is fed into successivevessels, the molecular weight and thus the intrinsic viscosity of thepolymer melt increases. The temperature of each vessel is generallyincreased and the pressure decreased to allow for a greater degree ofpolymerization in each successive vessel. However, to facilitate removalof glycols, water, alcohols, aldehydes, and other reaction products, thereactors are typically run under a vacuum or purged with an inert gas.Inert gas is any gas which does not cause unwanted reaction or productcharacteristics at reaction conditions. Suitable gases include, but arenot limited to, carbon dioxide, argon, helium, and nitrogen.

Once an It.V. of typically no greater than 0.35 dL/g is obtained, theprepolymer is fed from the prepolymer zone to a finishing zone where thesecond half of polycondensation is continued in one or more finishingvessels ramped up to higher temperatures than present in theprepolymerization zone, to a value within a range of from 280° C. to305° C. until the It.V. of the melt is increased from the lt.V of themelt in the prepolymerization zone (typically 0.30 dL/g but usually notmore than 0.35 dL/g) to an lt.V in the range of from about 0.50 dL/g toabout 0.70 dL/g. The final vessel, generally known in the industry asthe “high polymerizer,” “finisher,” or “polycondenser,” is operated at apressure lower than used in the prepolymerization zone, typically withina range of between about 0.8 torr and 4.0 torr. Although the finishingzone typically involves the same basic chemistry as the prepolymer zone,the fact that the size of the molecules, and thus the viscosity,differs, means that the reaction conditions also differ. However, likethe prepolymer reactor, each of the finishing vessel(s) is connected toa flash vessel and each is typically agitated to facilitate the removalof ethylene glycol.

The residence time in the polycondensation vessels and the feed rate ofthe ethylene glycol and terephthalic acid into the esterification zonein a continuous process is determined in part based on the targetmolecular weight of the polyethylene terephthalate polyester. Becausethe molecular weight can be readily determined based on the intrinsicviscosity of the polymer melt, the intrinsic viscosity of the polymermelt is generally used to determine polymerization conditions, such astemperature, pressure, the feed rate of the reactants, and the residencetime within the polycondensation vessels.

Once the desired It.V. is obtained in the finisher, the melt is fed to apelletization zone where it is filtered and extruded into the desiredform. The polyester polymers of the present invention are filtered toremove particulates over a designated size, followed by extrusion in themelt phase to form polymer sheets, filaments, or pellets. Although thiszone is termed a “pelletization zone,” it is understood that this zoneis not limited to solidifying the melt into the shape of pellets, butincludes solidification into any desired shape. Preferably, the polymermelt is extruded immediately after polycondensation. After extrusion,the polymers are quenched, preferably by spraying with water orimmersing in a water trough, to promote solidification. The solidifiedcondensation polymers are cut into any desired shape, including pellets.

As known to those of ordinary skill in the art, the pellets formed fromthe condensation polymers, in some circumstances, may be subjected to asolid-stating zone wherein the solids are first crystallized followed bysolid-state polymerization (SSP) to further increase the It.V. of thepolyester composition solids from the It.V exiting the melt phase to thedesired lt.V. useful for the intended end use. Typically, the It.V. ofsolid stated polyester solids ranges from 0.70 dL/g to 1.15 dL/g. In atypical SSP process, the crystallized pellets are subjected to acountercurrent flow of nitrogen gas heated to 180° C. to 220° C., over aperiod of time as needed to increase the It.V. to the desired target.

Thereafter, polyester polymer solids, whether solid stated or not, arere-melted and re-extruded to form items such as containers (e.g.,beverage bottles), filaments, films, or other applications. At thisstage, the pellets are typically fed into an injection molding machinesuitable for making preforms which are stretch blow molded into bottles.

As noted, metallic titanium particles may be added at any point in themelt phase or thereafter, such as to the esterification zone, to theprepolymerization zone, to the finishing zone, or to the pelletizingzone, or at any point between each of these zones, such as to meteringdevices, pipes, and mixers. The metallic titanium particles can also beadded to the pellets in a solid stating zone within the solid statingzone or as the pellets exit the solid-stating reactor. Furthermore, themetallic titanium particles may be added to the pellets in combinationwith other feeds to the injection molding machine or fed separately tothe injection molding machine.

If the metallic titanium particles are added to the melt phase, it isdesirable to use particles having a small enough d₅₀ particle size topass through the filters in the melt phase, and in particular thepelletization zone. In this way, the particles will not clog up thefilters as seen by an increase in gear pump pressure needed to drive themelt through the filters. However, if desired, the metallic titaniumparticles can be added after the pelletization zone filter and before orto the extruder.

Thus, according to the invention, metallic titanium particles of a widerange of d₅₀ particle sizes can be added either together with aphosphorus-containing compound to the esterification zone, theprepolymer zone, or at any point in between, or after the addition of aphosphorus compound to the esterification zone prior to completing theesterification reaction to the desired degree, or after the addition ofthe phosphorus compound to any zone and to a reaction mixture containingan active phosphorus compound. The point at which the metallic titaniumparticles are added, or the presence or absence of such other activecompounds in the melt, is not limited since the metallic titaniumparticles function to enhance the rate of reheat. The function of themetallic titanium particles as a reheat enhancing additive allows a wideoperating window and flexibility to add the metallic titanium particlesat any convenient point, even in the presence of activephosphorus-containing compounds in the melt phase.

Thus, the metallic titanium particles may be added together withphosphorus compounds either as a mixture in a feedstock stream to theesterification or prepolymer zone, or as separate feeds but added to thereaction mixture within the zone simultaneously. Alternatively, themetallic titanium particles may be added to a reaction mixture withinthe esterification zone after a phosphorus compound has been added tothe same zone and before completion of the esterification reaction.

Typical phosphorus-containing compounds added in the melt phase includeacidic phosphorus-containing compounds recognized in the art. Suitableexamples of such additives include phosphoric acid, phosphorous acid,polyphosphoric acid, carboxyphosphonic acids, and each of theirderivatives including acidic phosphate esters such as phosphate mono-anddi-esters and non-acidic phosphate esters such as trimethyl phosphate,triethyl phosphate, tributyl phosphate, tributoxyethyl phosphate,tris(2-ethylhexyl) phosphate, trioctyl phosphate, triphenyl phosphate,tritolyl phosphate, ethylene glycol phosphate, triethylphosphonoacetate, dimethyl methyl phosphonate, tetraisopropylmethylenediphosphonate, mixtures of mono-, di-, and tri-esters ofphosphoric acid with ethylene glycol, diethylene glycol, and2-ethylhexanol, or mixtures of each, among others.

In addition to adding metallic titanium particles to virgin polymer,whether to make a concentrate or added neat to the melt phase after theprepolymerization reactors or to an injection molding zone, metallictitanium particles may also be added to post-consumer recycle (PCR)polymer. PCR containing metallic titanium particles is added to virginbulk polymers by solid/solid blending or by feeding both solids to anextruder. Alternatively, PCR polymers containing metallic titaniumparticles are advantageously added to the melt phase for making virginpolymer between the prepolymerization zone and the finishing zone. Thelt.V. of the virgin melt phase after the prepolymerization zone issufficiently high at that point to enable the PCR to be melt blendedwith the virgin melt. Alternatively, PCR may be added to the finisher.In either case, the PCR added to the virgin melt phase may contain themetallic titanium particles. The metallic titanium particles may becombined with PCR by any of the methods noted above, or separately fedto and melt blended in a heated vessel, followed by addition of the PCRmelt containing the metallic titanium particles to the virgin melt phaseat these addition points.

Other components can be added to the compositions of the presentinvention to enhance the performance properties of the polyesterpolymers. For example, crystallization aids, impact modifiers, surfacelubricants, denesting agents, compounds, antioxidants, ultraviolet lightabsorbing agents, catalyst deactivators, colorants, nucleating agents,acetaldehyde reducing compounds, other reheat rate enhancing aids,sticky bottle additives such as talc, and fIIIers and the like can beincluded. The polymer may also contain small amounts of branching agentssuch as trifunctional or tetrafunctional comonomers such as trimelliticanhydride, trimethylol propane, pyromellitic dianhydride,pentaerythritol, and other polyester forming polyacids or diolsgenerally known in the art. All of these additives and many others andtheir use are well known in the art and do not require extensivediscussion. Any of these compounds can be used in the presentcomposition. It is preferable that the present composition beessentially comprised of a blend of thermoplastic polymer and metallictitanium particles, with only a modifying amount of other ingredientsbeing present.

Examples of other reheat rate enhancing additives that may be used incombination with metallic titanium particles include carbon black,antimony metal, tin, copper, silver, gold, palladium, platinum, blackiron oxide, and the like, as well as near infrared absorbing dyes,including, but not limited to, those disclosed in U.S. Pat. No.6,197,851, incorporated herein by reference.

The compositions of the present invention optionally may additionallycontain one or more UV absorbing compounds. One example includesUV-absorbing compounds which are covalently bound to the polyestermolecule as either a comonomer, a side group, or an end group. SuitableUV-absorbing compounds are thermally stable at polyester processingtemperatures, absorb in the range of from about 320 nm to about 380 nm,and are nonextractable from the polymer. The UV-absorbing compoundspreferably provide less than about 20%, more preferably less than about10%, transmittance of UV light having a wavelength of 370 nm through abottle wall 305 μm thick. Suitable chemically reactive UV absorbingcompounds may include, for example, substituted methine compounds.

Suitable compounds, their methods of manufacture and incorporation intopolyesters are further disclosed in U.S. Pat. No. 4,617,374, thedisclosure of which is incorporated herein by reference. TheUV-absorbing compound(s) may be present in amounts between about 1 ppmto about 5,000 ppm by weight, preferably from about 2 ppm to about 1,500ppm, and more preferably between about 10 ppm and about 500 ppm byweight. Dimers of the UV absorbing compounds may also be used. Mixturesof two or more UV absorbing compounds may be used. Moreover, because theUV absorbing compounds are reacted with or copolymerized into thebackbone of the polymer, the resulting polymers display improvedprocessability including reduced loss of the UV absorbing compound dueto plateout and/or volatilization and the like.

The polyester compositions of the present invention are suitable forforming a variety of shaped articles, including films, sheets, tubes,preforms, molded articles, containers and the like. Suitable processesfor forming the articles are known and include extrusion, extrusion blowmolding, melt casting, injection molding, stretch blow molding,thermoforming, and the like.

The polyesters of this invention may also, optionally, contain colorstabilizers, such as certain cobalt compounds. These cobalt compoundscan be added as cobalt acetates or cobalt alcoholates (cobalt salts orhigher alcohols). They can be added as solutions in ethylene glycol.Polyester resins containing high amounts of the cobalt additives can beprepared as a masterbatch for extruder addition. The addition of thecobalt additives as color toners is a process used to minimize oreliminate the yellow color, b*, of the resin. Other cobalt compoundssuch as cobalt aluminate, cobalt benzoate, cobalt chloride and the likemay also be used as color stabilizers. It is also possible to addcertain diethylene glycol (DEG) inhibitors to reduce or prevent theformation of DEG in the final resin product. Preferably, a specific typeof DEG inhibitor would comprise a sodium acetate-containing compositionto reduce formation of DEG during the esterification andpolycondensation of the applicable diol with the dicarboxylic acid orhydroxyalkyl, or hydroxyalkoxy substituted carboxylic acid. It is alsopossible to add stress crack inhibitors to improve stress crackresistance of bottles, or sheeting, produced from this resin.

With regard to the type of polyester which can be utilized, any highclarity, neutral hue polyester, copolyester, etc., in the form of aresin, powder, sheet, etc., can be utilized to which it is desired toimprove the reheat time or the heat-up time of the resin. Thus,polyesters made from either the dimethyl terephthalate or theterephthalic acid route or various homologues thereof as well known tothose skIIIed in the art along with conventional catalysts inconventional amounts and utilizing conventional processes can beutilized according to the present invention. Moreover, the type ofpolyester can be made according to melt polymerization, solid statepolymerization, and the like. Moreover, the present invention can beutilized for making high clarity, low haze powdered coatings. An exampleof a preferred type of high clarity polyester resin is set forth hereinbelow wherein the polyester resin is produced utilizing specific amountsof antimony catalysts, low amounts of phosphorus and a bluing agentwhich can be a cobalt compound.

As noted above, the polyester is produced in a conventional manner asfrom the reaction of a dicarboxylic acid having from 2 to 40 carbonatoms with polyhydric alcohols such as glycols or diols containing from2 to about 20 carbon atoms. The dicarboxylic acids can be an alkylhaving from 2 to 20 carbon atoms, or an aryl, or alkyl substituted arylcontaining from 8 to 16 carbon atoms. An alkyl diester having from 4 to20 carbon atoms or an alkyl substituted aryl diester having from 10 to20 carbon atoms can also be utilized. Desirably, the diols can containfrom 2 to 8 carbon atoms and preferably is ethylene glycol. Moreover,glycol ethers having from 4 to 12 carbon atoms may also be used.Generally, most of the commonly produced polyesters are made from eitherdimethyl terephthalate or terephthalic acid with ethylene glycol. Whenpowdered resin coatings are made, neopentyl glycol is often used insubstantial amounts.

Specific areas of use of the polyester include situations whereinpreforms exist which then are heated to form a final product, forexample, as in the use of preforms which are blow-molded to form abottle, for example, a beverage bottle, and the like. Another use is inpreformed trays, preformed cups, and the like, which are heated anddrawn to form the final product. Yet another use relates to polyesteryarn which is forced through a plurality of spinnerets having aninfrared quench collar thereabout. Additionally, the present inventionis applicable to highly transparent, clear and yet low haze powderedcoatings wherein a desired transparent film or the like is desired.

This invention can be further illustrated by the following examples ofpreferred embodiments, although it will be understood that theseexamples are included merely for purposes of IIIustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated.

EXAMPLES

The titanium (Ti) metal particles used in the examples were obtainedfrom Argonide Nano-materials Technologies. The particles had a d₅₀particle size of about 50 nm with a relatively narrow particle sizedistribution.

The polymer used in the examples was commercial grade PET Voridian™ CM01Polymer, which is a PET copolymer containing no reheat additive. Thetitanium metal particles were added into virgin CM01 during meltcompounding. First, a concentrate containing 416 ppm titanium metalparticles was made using a one-inch single screw extruder with saxtonand pineapple mixing head. The extruder was also equipped withpelletization capability. The concentrate was then crystallized using atumbling crystallizer at 170° C. for 1 hour. The crystallizedconcentrate was then let down into CM01 virgin polymer with the finalconcentration of titanium metal in CM01 ranging from 2 ppm to 15.4 ppm.During the compounding process, CM01 virgin polymer was used to purgethe extruder barrel several times to ensure no cross contaminationoccurred between different batches. Finally, the CM01 polymers withdifferent levels of titanium metal particles was injection molded intotwenty-ounce bottle preforms using a BOY (22D) injection molding machineoperated under standard molding conditions.

In the examples, the reheat of a given polyester composition wasmeasured by twenty-ounce bottle preform Reheat Improvement Temperature(RIT). In order to determine the RIT of each composition, all preformswere run through the oven bank of a Sidel SBO2/3 blow molding unit in aconsistent manner. The lamp settings for the Sidel blow molding machineare shown in Table 1. The reheat time was 38 seconds, and the poweroutput to the quartz infrared heaters was set at 64%. A series of fivepreforms was passed in front of the quartz infrared heaters and thepreform surface temperature was measured. As mentioned earlier, in theexamples, the reheat rate of a given composition was measured by preformreheat improvement temperature (RIT). The preform reheat improvementtemperature was calculated by comparing the difference in preformsurface temperature of the target samples with that of the virgin CM01.The higher the RIT value, the higher the reheat rate of the composition.

The concentration of titanium metal particles in CM01 was determined byInductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) usinga Perkin-Elmer Optima 2000 instrument. Differential Scanning Calorimetry(DSC) was used for crystallization half time (t_(1/2)) measurements. Anisothermal crystallization kinetics experiment is performed using aPerkin-Elmer Pyris 1 using helium as a purge gas. The calorimeter iscalibrated using indium and tin standards. A 10 mg sample is heated at500° C./min from room temperature to 290° C. and held at temperature for2 minutes. The sample is then control cooled at 500° C./min to the testtemperature. The exothermic crystallization event is followed as afunction of time and the time of peak exothermic activity is identifiedas the half-time of crystallization (ta/_(1/2)). The same sample is usedto generate half-times for all temperatures desired, in decreasing orderin 10° C. increments between 200° C. and 140° C.

Color measurements were performed using a HunterLab UltraScan XE (HunterAssociates Laboratory, Inc., Reston Va.), which employs diffuse/8°(illumination/view angle) sphere optical geometry. The color scaleemployed was the CIE LAB scale with D65 illuminant and 10° observerspecified. Preforms with a mean outer diameter of 0.846 inches and awall thickness of 0.154 inches were measured in regular transmissionmode using ASTM D1746, “Standard Test Method for Transparency of PlasticSheeting.” Preforms were held in place in the instrument using a preformholder, available from HunterLab, and triplicate measurements wereaveraged, whereby the sample was rotated 90° about its center axisbetween each measurement.

Color in transmission at any thickness can be recalculated according tothe following:

T_(h) = T_(o)10^(−β h)$\beta = \frac{\log_{10}\left( {T_{o}/T_{d}} \right)}{d}$where

-   T_(h)=transmittance at target thickness-   T_(o)=transrnitance without absorption-   β=Absorption coefficient-   T_(d)=transmittance measured for sample-   h=target thickness-   d=thickness of sample

Table 2 and FIG. 1 show the correlation between the concentration ofmetallic titanium particles and the reheat improvement temperature(RIT), from which one can see that 15.4 ppm titanium is needed toachieve a RIT of 14.8° C.

TABLE 2 Impact of titanium metal particles on twenty-ounce bottlepreform reheat improvement temperature (RIT) and color. Sam- Ti MeasuredTi Preform ple d₅₀ concentration RIT No. System (um) (ppm) (° C.) L* a*b* 1 CM01 NA 0 0.0 83.3 −0.5 2.5 2 Ti + CM01 0.05 2 2.8 79.7 −0.4 2.3 3Ti + CM01 0.05 4.2 5.7 77.6 −0.3 2.4 4 Ti + CM01 0.05 15.4 14.8 62.5 0.12.6

FIG. 1 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform reheat improvementtemperature (RIT).

Correlations between titanium metal particles concentration and preformcolor properties are shown in FIGS. 2-4, from which one can see thattitanium metal particles led to satisfactory preform L*, a*, and b*values.

FIG. 2 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform L* value.

FIG. 3 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform a* value.

FIG. 4 depicts the correlation between titanium metal particleconcentration and twenty-ounce bottle preform b* value.

The impact of titanium metal particles on preform ltV is also shown inTable 3, from which one can see no significant preform ltV changeresulted due to the addition of titanium metal particles.

TABLE 3 Impact of titanium metal particles on twenty-ounce bottlepreform ItV. Measured Ti Sample No. System concentration (ppm) PreformItV 5 CM01 0 0.767 6 Ti + CM01 2 0.764 7 Ti + CM01 4.2 0.756 8 Ti + CM0115.4 0.729

The impact of the metallic titanium particles on the crystallizationkinetics is shown in Table 4 and FIG. 5. Based on these analyses, it isclear that the addition of these particles has only slightly changed thecrystallization kinetics of virgin PET. This result indicates that theaddition of titanium metal particles wIII not significantly increase thecrystallization kinetics of the preform during the reheating process,which will enable a bottle with low level of crystalline haze to beblown.

TABLE 4 Correlation between titanium metal particle concentration andcrystallization half time (t_(1/2)). Measured Ti Sample concentrationDSC t½ (minute) No. System (ppm) 200° C. 190° C. 180° C. 170° C. 160° C.150° C. 140° C. 9 CM01 0 — — 2.08 1.83 1.80 2.28 4.18 10 Ti + CM01 23.99 2.34 1.49 1.19 1.13 1.39 2.94 11 Ti + CM01 4.2 5.89 3.22 2.14 1.671.62 1.98 3.47 12 Ti + CM01 15.4  4.4 2.56 1.63 1.28 1.12 1.37 2.26

FIG. 5 depicts the crystallization half time (t_(1/2)) results forsystems with different levels of titanium metal particles.

1. A beverage bottle preform having improved reheat, comprising: apolyester polymer; and metallic titanium particles, having a medianparticle size from about 0.005 μm to about 100 μm, dispersed in thepolyester polymer.
 2. A beverage bottle comprising: a polyester polymer;and metallic titanium particles, having a median particle size fromabout 0.005 μm to about 100 μm, dispersed in the polyester polymer. 3.The beverage bottle preform of claim 1, wherein the metallic titaniumparticles are present in an amount of from 5 ppm to 50 ppm, with respectto the total weight of the beverage bottle preform.
 4. The beveragebottle preform of claim 1, wherein the polyester polymer comprisespolyethylene terephthalate.
 5. The beverage bottle preform of claim 1,wherein the metallic titanium particles have a median particle size from0.02 μm to 10 μm, and provide the beverage bottle preform with a reheatimprovement temperature (RIT) of at least 5° C. while maintainingpreform L* value of 60 or more.